Slip-way beacon



l May 31, 1938. E KFMMMQl 2,118,929

' SLIP-WAY BEACON Filed March '7, 1935 Fw L a APatented May 31, 1938 SLIP-WAY BEACON Ernst Kramar, Berlin-Tempelhof, Germany, assignor to C. Lorenz Aktiengesellschaft, Berlin- Tempelhof, Germany, a German company Application March 7, 1935, Serial No. 9,808 In Germany March 1, 1934 3` Claims;

The invention is an improvement upon that disclosed in the copending patent application Ser. No. 722,470, led April 26, 1934:,` for System for landing aeroplanes. In this application, a slipway beacon is described the essential features of which are that an additional signal is transmitted to the aeroplane as soon as this reaches the point where it should begin to descend, and that the landing is effected in accordance with the indication of eld intensity which the receiver shows at the moment of the reception of the additional signal. This method has the advantage that the receiver need not at the commencement of the flight be adjusted to have a predetermined sensitivity, but that it is quite insignicant what a sensitivity the receiver may have. The receiver should merely be of such a constancy that its sensitivity is not varied during landing, that is during the time which there is between the moment of beginning the descent and the moment of touching the ground.

In order to decrease as far as. possible the expenditure in apparatus, the additional signal will preferably be transmitted by wireless on the same or approximately the same wavelength as is used for characterizing the gliding path. This path and the additional signal are differentiated from each other with the aid of different characteristic tones.

The invention described hereafter proposes in this connection to polarize the two radiations dierently with respect to one another. In this way, above all a considerable simplification of the entire arrangement is attained on the transmitter side.

For the gliding path a vertical polarization is employed, in order to create a good slip-way guide by means of a simple antenna arrangement comprising, for instance, a dipole continuously fed by a high-frequency generator, and two reflector dipoles keyed alternately. This is especially so if a dipole, fed continuously, and reflector dipoles are disposed in a position so high above the ground that a propagation curve suitable for the gliding path is obtained without additional devices being requisite. If according to the invention a horizontally disposed dipole is employed for the additional signal, then a discshaped radiation is attained without the aid of additional means, namely a radiation vertical to the direction in which the aircraft is moving, provided that the dipole is located in this. direction.

The application on the transmitter side of these different polarizations results on the receiving side (Cl. Z50-11) in the necessity for operating with receivingantennas polarized essentially in the same manner. The antennas. employed on the receiving side, which in most cases are dipoles, are in accordance with another feature of the invention preferably connected With separate audion stages. In order that also on the receiving side the entire arrangement become as simple as possible, one could intend to produce gliding path and additional signal on the basis` of the same wavelength and to distinguish between them by different tones. One could intend also to ensure that the carrier frequencies for gliding path and additional signal differ from each other slightly. This would result in the advantage that the constancy of the transmitters need not be so great as in the case of the same wave length. In this event, however, on the receiving side an input resonance circuit or receiver circuits would have to be employed, these circuits being so wide as to allow the two carrier frequencies to pass through with the best constant efficiency. On the other hand, however, the superposing-tones of the transmitters must be considerably higher than the characteristic tones. This method would require the least expenditure on the receiving side, if the transmission energy and thus the intensity of the receiving field are very great, In practice, however, it is for several reasons sought with respect to the transmitter side to be successful with the aid of means as simple as possible. The described method may then happen to be insufflcient. In view of this possibility, the invention further proposes to provide separate audion stages in the receiver. This has the advantage that each carrier wave can be received by means of sharply tuned circuits in employing back coupling or dispensing with attenuation, a method that in the case of a wide resonance curve can of course not be adopted immediately. The low frequency may then be gathered at a place after the audion, so that also here the expenditure on the receiving side will not be especially great.

The invention will be more fully explained in the following description taken in conjunction with the drawing in which Fig. 1 shows the gliding path in a horizontal section, Fig. 2 in a vertical section and Fig. 3 the appertaining receiving arrangement. l

In Fig. 1 the landing ground is indicated b AP. The gliding path is obtained by a transmission arrangement consisting of a continuously energized vertical dipole D and two alternately keyed reflectors Rl and R2. Two shifted ellipse diagrams are alternately eifective, said diagrams ranged in the landing direction. A disc-shaped radiation diagram in the form of SI is effected vertically to the flying direction.

Fig. 2 represents a gliding path method in the vertical plane and marks the landing ground also with AP, the Vertical dipole for the gliding path radiation with D and the horizontal dipole with DI. The gliding path curve GI, G2 and G3 are lines of equal field intensity of the vertically polarized gliding path radiation and the diagram` Si represents a horizontally polarized signal. The airplane approaches e. g. at a height h, ascertained by means of the barometer-altimeter and intersects. the radiation of the presignal Si. The pilot knows thus that he may initiate the landing and flies e. g. on the curve of constant field intensities Gl.

Fig. 3 shows the receiving arrangement. The vertically polarized gliding path radiation is received by means of a vertical dipole El, is ampliled in the high frequency amplier H, rectified inthe audion part Al, amplied at low frequency in the member N and conducted to the indicating instrument J or the telephone T respectively. The horizontally polarized signals are received by means of the horizontal dipole E2, rectied in the second audion part A2 Vand conducted to the common low frequency amplifier N.

What is claimed is:

1. In a slip-way beacon wherein the point at which the descent for landing should be commenced along a gliding path'is indicated to the aircraft by an additional signal transmitted by wireless, the method of aiding the landing of aircraft which comprises transmitting vertically polarized radiations for the gliding path and transmitting horizontally polarized radiations for the additional signal in a plane normal to the direction of landing of said aircraft. Y

2. The method of landing aircraft according to claim 1 which includes the steps of separately detecting the gliding path signal and the additional signal and thenV impressing Vsaid detected signals upon a common signal amplifying path.

3. The method of landing aircraft according to claim l, wherein approximately the same wave length is employed for both radiations.

ERNST KRAMAR. 

